I had that light in 2 versions. 20" on a 10 gallon and 24" on a 20 high. I think you will need ferts and C02. You could try toning down the intensity by using one or two layers of window screen if its too much.

This is only my personal experience and some people won't like it but here goes -

I had two of these fixtures on low tech (no real fert regimen, no CO2 or excel dosing) and I got bad algae on the surface of everything. Plant leaves, rocks, etc.

What I ended up doing (because I am lazy and because I was more worried about my shrimp than about plant growth) is that I tossed in enough floaters (frogbit being my favorite) to cover a good portion of the top of the tank.

This probably cut the visual spectrum of light hitting the substrate in half. I never bothered to measure PAR.

Between the floaters blocking light from the tank and the floaters sucking up nutrients like crazy (and not needing much CO2 since they have access to atmosphere) my algae problems went away pretty quickly and never came back.

The downside to this method is that it can make getting good growth of rooted plants difficult since the floating plants outcompete substrate level plants so easily in this situation.

There is probably a way to manage a balance of sorts but I never bothered to try.

I run the 6 bulb 48" version of that light 31 inches from the substrait. I only run two of the bulbs though so it would be the same as your fixture. Expect the potential for all types of algea, Its a very strong light. I ended up high co2, high fert and I have frogbit and lilly pads covering the waters surface to help cut the light also, but i have ran the full spectrum of algea. I have a few tufts of brush algea on the back ground left. For me changes in lighting you can see results good or bad with in a 24 hour period where CO2 and ferts results take more time.

I use tap also...but same light fixture being the only thing in common will not determin algea or no algea, unless we all had exact same water fish load, ferts co2 we could say it was too much light, my case was too much light, I could have put more CO2 in the water but I want to keep my fish alive.

hey now I have a question concerning algea. I have an aquaticlife T5ho 30" on my 20 gal L I have a clear glass canopy and the fixture is 3" above the clean cover. I use 2 mil of excel daily. and the regular seachem schedule of iron, potassium and the regular flourish. The light is on 8 hours a day. I've got 1 oto in the tank. You'd think I'd have algea but I don't. How come? It couldn't be that measley little bit of excel daily or could it?

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